In recent years, it is common to control the state of equipment using an embedded system. For example, a computer mounted on an automobile is called ECU (electric control unit), and performs various controls related to running. The control computer in such an embedded system is widely used in fields other than the automobile such as a plant, a production line, or the like.
In the control computer represented by ECU, it is necessary to guarantee that a program operates according to specifications properly. This is because, when an unexpected operation occurs due to the breakdown of a circuit or the failure of the program, it becomes impossible to normally control a vehicle or a line so that safely of a user is threatened.
In the control computer, a self-diagnosis function is often provided in order to prevent an accident caused by the breakdown or failure. In the case of the automobile, the self-diagnosis function is called “Diagnosis” or “OBD (On-board diagnostics)” (see Non Patent Literature 1). The self-diagnosis function is capable of detecting an abnormal state such as the occurrence of an undefined signal or the like in the computer, and issuing an alarm to a user, stopping the system, and recording log information.